They're trying to get invalidation of patent on record. And it does make sense, as plaintiff can refile (ostensibly after they sue a few others and get precedent in place)
I agree that invalidating the patent is a strong motivation, but I imagine that another major motivation is in establishing their reputation. Future putative litigants will think twice about getting dragged into a legal battle with a company that doesn't let them walk away from a battle when it no longer suits them.
Where do you see Newegg asking for the troll's patent to be invalidated?